Right-clicking panels turns them black when Vulkan is the selected Graphics API

How to reproduce:
1. Create a new Unity project using the 3D Template
2. Navigate to Edit > Project Settings... > Player
4. Disable "Auto Graphics API for Windows" under "Other Settings"
5. Click the "+" sign and add Vulkan, then drag it above the default Graphics API and click "Restart Editor"
6. Right-click panel "Hierarchy" or "Project Browser"

Expected result: Right-clicking panels does not turn them black
Actual result: Right-clicking panels turns them black

Reproducible with: 2018.4.28f1, 2019.4.13f1, 2020.1.10f1, 2020.2.0b9, 2021.1.0a2

Notes: Reproduces upon clicking panels 3/5 times